A variety of approaches have been developed for measuring surface topography optically. For example, optical systems and methods have been developed and employed that can be used to optically measure surface topography of a patient's teeth. The measured surface topography of the teeth can be used, for example, to design and manufacture a dental prosthesis and/or to determine an orthodontic treatment plan to correct a malocclusion.
One technique for measuring surface topography optically employs laser triangulation to measure distance between a surface of the tooth and an optical distance probe, which is inserted into the oral cavity of the patient. Surface topography measured via laser triangulation, however, may be less accurate than desired due to, for example, sub-optimal reflectivity from the surface of the tooth.
Other techniques for measuring surface topography optically, which are embodied in CEREC-1 and CEREC-2 systems commercially available from Siemens GmbH or Sirona Dental Systems, utilize the light-section method and phase-shift method, respectively. Both systems employ a specially designed hand-held probe to measure the three-dimensional coordinates of a prepared tooth. Both of these approaches, however, require a specific coating (i.e. measurement powder and white-pigments suspension, respectively) to be deposited on the tooth. The thickness of the coating layer should meet specific, difficult to control requirements, which can lead to inaccuracies in the measurement data.
In yet another technique, mapping of teeth surface topography is based on physical scanning of the surface by a probe and by determining the probe's position, e.g., by optical or other remote sensing means.
U.S. Pat. No. 5,372,502 discloses an optical probe for three-dimensional surveying. Various patterns are projected onto the tooth or teeth to be measured and a corresponding plurality of distorted patterns are captured by the optical probe. Each captured pattern can be used to refine the topography measurement.